SRAM XX

XX, Revealed

SRAM's been making mountain bike parts for 21 years, but there hasn't been a complete SRAM mountain bike groupset until now. Sure, you've been able to kit your bike completely with parts from SRAM subsidiaries since 2004, when SRAM purchased brakemaker Avid, but the new group is a major step forward. "We learned a lot developing our road groups," says Ron Ritzler, SRAM's mountain bike category manager, "and we said, 'What would happen if we went into [mountain bike parts] with a similar no-holds-barred attitude on development?"

That change in thinking describes what sets XX apart from past SRAM efforts. The company pulled together design and engineering resources from SRAM offices in Germany, Chicago, Colorado Springs and San Luis Obispo—teams that usually don't work closely together. "Not that we had blinders on to the other groups [before], but the idea is that we're experts within a specialty," explains Sander Rigney, product manager for RockShox suspension. "The XX development is the first time we've spanned all locations and development groups."

The XX group's weight, gearing and design clearly target the performance XC segment. Wisely, SRAM left enough wiggle room to also appeal to the ultralight trail or all-mountain bike segments (the Scott Genius or Specialized Enduro SL rider who wants a six-inch-travel bike that weighs less than 26 pounds). As of this writing, SRAM wasn't prepared to disclose exact component or overall group weights, but a leaked document in February targeted a total weight of less than 2,300 grams, a significant decrease on existing groups. (Go to mountainbike.com/xx for updates on the weight.)

The result is a group that emphasizes integrated performance above all, even including suspension. XX preserves an impressive array of options for the rider—necessary to work with the myriad standards competing today—but is clearly designed to work best as a unit. Here, we present the first extensive look at what XX offers.

Drivetrain: 2x10
The most obvious change with XX is the move to a road-like 2x10 drivetrain. The potential advantages of 2x10 are crisper shifting, lighter weight, more useable gear combinations and narrower Q-Factor. Perhaps most important to Ritzler: It cleans up the mess that is mountain bike shifting. "Front shifting in particular is what mountain bikes don't like to do," he says. According to him, 2x10 overcomes a key weakness of triple chainrings simply because there's no middle ring trying to accommodate both up- and downshifts. On its two-ring system, SRAM was able to double the number of ramps and pins to assist upshifts. Ritzler predicts that front shifting will be XX's "knockout punch."

To get a gearing range similar to 3x9 (see "The Ultimate Gear Comparison," p. 50), SRAM had to boost its cassette options to include a massive 11-36. Even so, Ritzler thinks most buyers will need 26/39 chainrings rather than 28/42 since the former is a combo better suited for climbing.

Like the Powerdome cassette in SRAM's Red group, XX's X-Glide cassette is machined from a single piece of steel, but is laced with dozens of cutouts to shed mud and drop weight. The largest cog is aluminum and is lightly press-fit to the main unit for replaceability. The 11-tooth steel cog is also separate. To handle the extra chain wrap needed, the mid-cage rear derailleur uses an offset top pulley.

Key Drivetrain Features

18 useable gears (all 10 in the large ring; all but the two smallest in the small ring)

Brakes: Elixir Remix
When Avid released its Elixir brake last year, it was clear the company was enthusiastic about its prospects. But one major hurdle remained: weight. The Taperbore cylinder design resulted in a relatively large lever body and a 375-gram weight with a 160mm rotor.

For XX, SRAM shortened the Taperbore cylinder and lever body by incorporating the spring around the push rod. "We've effectively used the space inside the lever body twice," says Avid product manager Paul Kantor. The whole unit is now forged from magnesium. The reach adjustment knob on the Elixir CR is replaced with a 2mm hex bolt, and the carbon lever blade was put on a diet.

SRAM kept power and modulation intact by using the same piston diameters as Elixir as well as a fixed lever blade pivot, which offers a more "direct" feel, says Kantor. The two-piece caliper is magnesium, and the multi-material rotor uses a steel brake track on an aluminum carrier, in six-bolt and center-lock options."

All of that pared the weight significantly for the full-adjustable system to less than the just-introduced Elixir CR mag—now SRAM's lightest brake, at 330 grams—which does not have the multi-material rotor. There's an option for the integrated XLoc hydraulic fork lockout (more on that in "Handlebar Controls," below) on the right or left lever, or as an aftermarket upgrade.

Key Brake Features

Forged magnesium lever body and two-piece caliper

Carbon-fiber brake-lever blade

Adjustable reach and pad contact

Taperbore master cylinder technology

Rotor Sizes

140 (rear), 160, 185mm

Handlebar Controls: More Than Shifters
SRAM's principal goal with the controls was to preserve the maximum amount of adjustability. "[The final result] is actually more conservative than what we set out to do," says Kantor. "We had a ton of ideas, but they required us to take so much control of your bike that we weren't comfortable doing that. We wanted people to be able to upgrade their current mountain bike."

Chief among the advancements is MatchMaker X, the next generation of the MatchMaker unified shift-/brake-lever clamp. It uses a one-bolt U-clamp for ease of installation and allows the user to mount the shifters in- or outboard of the brake levers. The XX shift levers retain the adjustable paddle function from X.O but, as Ritzler puts it, the whole unit has "been kind of 'nano'd' and shrunk down."

But perhaps the most impressive achievement is the XLoc suspension lockout. When looking at the handlebar, says RockShox's Rigney, first priority is always given to brake position, then shifters. Any suspension element like lockout is a distant third, and made more problematic by the large spool needed to wind or unwind a cable-activated unit. "You can angle it or wrap it," says Rigney, "but you're still taking up a chunk of space." The XX team's response: Get rid of the spool by going hydraulic.

The XLoc relies on a poppet-style valve, like a ballpoint pen, to open the compression circuit. Blowoff is adjustable at the remote lockout, and the system uses suspension fluid, but the lockout circuit and the compression and rebound circuits remain separate, sealed units—only the valve that controls blowoff is directly connected to the XLoc, and then only mechanically, with no oil pass-through. SRAM discovered that, with hydraulics, there was none of the lag that occurred when releasing a cable-activated lockout under pressure.

Because of that, Rigney considers the whole system as flipping lockout onto its head: Instead of locking out the fork when you don't want it to move, the fork's normal state is locked and you click the poppet valve to unlock it only when needed. The system is obviously scaleable to rear suspension as well and, while Rigney declined to discuss specifics, he did say, "I think it's pretty obvious what we're thinking about next."

Key Handlebar Control Features

Right- or left-brake-compatible XLoc options

One-bolt U-clamp MMX

Hydraulic lockout

Remote-adjustable floodgate for blowoff

XLoc-Compatible Fork Platforms

Reba, Revelation, SID and SID World Cup

What's Next for XX?XX is arguably the first group that truly pulls together every corner of SRAM's vast manufacturing empire. The group is loaded with small, thoughtful touches, ranging from the slight angle on the XLoc as it comes off the handlebar to the fact that, within reason, every part on the bike installs with a T25 TORX fastener. But with all this talk of integration, the piece currently missing from XX is the one place where suspension, drivetrain and brakes all must integrate: the wheels.

With its acquisition of Zipp (and, prior to that, Sachs), SRAM has assembled a formidable array of wheelbuilding resources. As a result, the XX group could benefit from further developments, from integrating rotor attachments and cassette splines to fork/axle interfaces. But for now, at least, no hoops are on the horizon. When pressed, Ritzler would say only, "I wouldn't be surprised to see that in the future."